Catalysts used in FCC processes are in particle form, usually have an average particle size in the range of 20 to 200 microns, and circulate between a cracking reactor and a catalyst regenerator. In the reactor, hydrocarbon feed contacts hot, regenerated catalyst which vaporizes and cracks the feed at about 400° C. to 700° C., usually 500° C. to about 550° C. The cracking reaction deposits carbonaceous hydrocarbons or coke on the catalyst, thereby deactivating it. The cracked products are separated from the coked catalyst. The coked catalyst is stripped of volatiles, usually with steam, in a catalyst stripper and then regenerated. The catalyst regenerator burns coke from the catalyst with oxygen containing gas, usually air, to restore catalyst activity and heat catalyst to, e.g., 500° C. to 900° C., usually 600° C. to 750° C. The hot regenerated catalyst recycles to the cracking reactor to crack more fresh feed. Flue gas from the regenerator may be treated to remove particulates or convert CO, and then discharged into the atmosphere. The FCC process, and its development, is described in the Fluid Catalytic Cracking Report, Amos A. Avidan, Michael Edwards and Hartley Owen, in the Jan. 8, 1990 edition of the Oil & Gas Journal.
The product distribution from current FCC processes comprises a number of constituents, with gasoline being of primary interest to most refiners. Light olefins and LPG are also found in the FCC product, and are increasingly becoming of interest to refiners as those products become more valuable. The light olefins produced can be used for a number of purposes, e.g., they are upgraded via sulfuric or HF alkylation to high quality alkylate. LPG is used for cooking and/or heating purposes. Accordingly, operators of FCC units can vary the content of their products depending upon the markets they are serving and the value associated with each of the components found in an FCC product.
Propylene is a particular light olefin in high demand. It is used in many of the world's largest and fastest growing synthetic materials and thermoplastics. Refiners are relying more and more on their FCC units to meet the increased demand for propylene, thus shifting the focus of the traditional FCC unit away from transportation fuels and more toward petrochemical feedstock production as operators seek opportunities to maximize margins.
If a refinery cannot expand its existing unit, FCC operators have rather limited options for increasing light olefin production. Reported options include:                a. FCC processes employing ZSM-5 and large pore zeolite that share matrix, i.e., an integral catalyst.        b. FCC processes using additive ZSM-5 catalyst.        c. Production of cracked gas from gas oil over pentasil zeolites at high cracking severity.        
U.S. Pat. No. 3,758,403 discloses adding ZSM-5 to conventional large pore zeolite cracking catalyst formulations, including adding ZSM-5 during manufacture of the large pore zeolite catalyst particles so that the ZSM-5 is integrated into the catalyst particle. Based on U.S. Pat. No. 3,758,403, use of large pore zeolite cracking catalyst containing large amounts of ZSM-5 additive that has been integrated into the catalyst gives only modest increases in light olefin production. A 100% increase in ZSM-5 content (from 5 wt % ZSM-5 to 10 wt % ZSM-5) increased the propylene yield less than 20%, and decreased slightly the potential gasoline yield.
U.S. Pat. No. 6,566,293 discloses another type of integral catalyst wherein phosphorus is combined with the ZSM-5 and calcined prior to their addition to matrix, and optionally, and in certain instances, preferably large pore zeolite Y. The resulting slurry of calcined ZSM-5/phosphorus and matrix-containing slurry is then spray dried into catalyst. The U.S. Pat. No. 6,566,293 patent reports that these catalysts are efficient in olefins production, while also maintaining bottoms cracking. See also “FCC Meets Future Needs”, Hydrocarbon Engineering, January 2003.
U.S. Pat. No. 7,517,827 discloses a process for preparation of LPG selective catalyst particles comprising a medium pore low soda zeolite bonded with clay-phosphate-silica-alumina binder. The catalyst suitable for cracking heavy residual hydrocarbon feeds.
US 2013/0023710 A1 discloses a FCC additive preparation process and composition, which has high efficiency in the production of light olefins C2, C3 and C4 hydrocarbons, specifically propylene and it also discloses the stabilization of medium pore zeolite specifically ZSM-5 using optimum phosphate salts at a pH in the range 7-9 with synergetic combination of silica rich binder to produce FCC additive having excellent stability under severe hydrothermal conditions.
U.S. Pat. No. 6,858,556 teaches the preparation of stabilized dual zeolite in a single particle catalyst composition consisting of 5% ZSM-5 and 12% REY using conventional silica-alumina binder for cracking of heavier hydrocarbons into lighter products.
Following patents i.e., U.S. Pat. Nos. 5,220,089, 5,243,121, 6,156,947, 4,309,280, 4,803,185, 4,522,705, 4,784,745, 4,828,679, 4,927,523, 4,927,526, 4,983,276, 4,997,545, 5,039,640, 5,302,567, 5,779,882, 5,997,728, 6,613,710, 6,677,263, 5,234,575 illustrate prior art processes and compositions which are different from present invention with respect to FCC composition, process and performance.
The available prior art compositions though possess catalytic properties but there is always a need to produce improved catalyst additives that are capable of producing enhanced yields of liquefied petroleum gas and light olefins as compared to the available conventional catalyst compositions.